It is now common for people to listen to music using mobile devices such as smartphones or other mobile media players (collectively “smartphones”). Users have rapidly become accustomed to having music or other audio played back through such devices, and often tend to have their smartphones with them at all times. In some instances, users may wish to play the audio through loudspeakers rather than through headphones.
Due to the small size of smartphones, loudspeakers contained within a smartphone must also be small. There are a also number of small and portable external loudspeakers available that may be used to reproduce the audio output from a smartphone; such external loudspeakers may be connected to a smartphone by, for example, a physical connection such as a wire or by a wireless connection such as Bluetooth, a known wireless technology standard.
In some instances, a smartphone may have the capability of applying an equalizer to the audio output; the equalizer is a circuit that allows for adjustment of the balance between frequency components of the audio signal, and thus the frequency response of the loudspeaker(s). In some cases, the equalizer may have preset functionality, while in other cases the it may be a graphic equalizer that allows the user to see a visual representation of the frequency response and adjust it using “sliders” that can alter the response in different frequency bands. Equalization may be done for various reasons, including satisfying the user's particular aesthetic preferences for, for example, more or less bass or treble in the reproduced audio.
Smartphones may also include compandors (also known as a compander). A compandor is a circuit for compressing or expanding a signal or some portion thereof. In smartphones, they often have two different purposes. One purpose is to protect the loudspeakers from damage when the loudspeaker temperature is too high, or from signals that are too large at a resonant frequency of the loudspeaker. Signals that are too large many cause the diaphragm of the speaker to exceed its maximum displacement or excursion limit. Another purpose is to adjust the output level to make the audio more pleasing to the user by increasing the output level of quiet signals and decreasing the output level of very loud signals.